This invention relates to enhancing the processing capabilities of a core satellite communication system, and more particularly relates to such a system in which supplemental processing can be performed aboard a supplemental satellite launched after the core satellite.
The long operational lifetimes of orbiting communication satellites or spacecraft present a dilemma for designers of the electronic systems included in such spacecraft. Large, high capacity spacecraft are expensive, and their associated launch costs are substantial. As a result, there is a tendency to procure the largest, longest lifetime spacecraft possible.
However, deploying spacecraft with the longest lifetime possible presents problems in the context of the present communications industry which is changing rapidly and which is expected to serve new markets and provide new services in the not too distant future. However, the details of the new markets and services are not clear and have not been defined. With spacecraft communications in such a state of flux, some consultants have publicly advised against deploying spacecraft with operational lifetimes longer than about five years.
The current preference in commercial communication spacecraft is for bent-pipe transponders. Although it appears that there will eventually be a market for digital switching (circuit or cell switching), especially in the domestic Comsat band (Ka-band), the form of such a market is not clear. There is a need for an approach which allows deployment of large, expensive spacecraft optimized for the current bent-pipe paradigm (perhaps with on-board intermediate frequency (?IF≅) switching and including an alterable basic functionality which can be changed at a future time to a new form that might not exist at the time of launch.
Communication satellites are generally deployed in a defined orbital slot which consists of a geographical location and a band of frequencies which are authorized for receipt and transmission of communication signals. The acquisition of an orbital slot requires substantial effort and expense. There is a need for communication circuit techniques which enable the investment in an orbital slot to be protected by changing the processing function of an initial core spacecraft which is assigned to the orbital slot.
There also is a need for techniques which permit a spacecraft""s communication processing to be altered functionally, possibly multiple times, during its operational lifetime. The present invention enables the processing functionality to be altered with a degree of economy and ease which is not available by using any of the known prior techniques.
One object of the present invention is to provide components which can be placed on a core or initial satellite and which enable and facilitate communication with a supplemental satellite launched after the core satellite is placed into an orbital slot.
Another object of the invention is to provide components suitable for launching on a core satellite which perform immediately upon deployment, but which facilitate communication with additional components launchable with a less expensive supplemental satellite if there is a need for a change in processing functionality of the core satellite.
Yet another object of the present invention is to provide components suitable for launching with a core satellite to allow communication with a supplemental satellite on which a new processing function can be carried out, but which does not require duplication of the uplinks and downlinks built into the core satellite.
By using a component arrangement of the foregoing type, unprocessed or semi-processes signals received by the core satellite may be routed to a supplemental satellite over an intersatellite link where they are processed. The process outputs then may be sent back to the core satellite over the intersatellite link and inserted to a downlink signal chain for downlink transmission.
In one embodiment of the invention, there is an uplink receiver which is deployable with a first satellite and which is capable of receiving communication signals from a ground based communication station. A first processor, such as a bent pipe repeater, is deployable on the first satellite and is capable of processing signals from the uplink receiver. An intersatellite communications link terminal, deployable with the first satellite, is capable of transmitting signals to a second processor deployable with a second satellite launched after the first satellite and is capable of receiving signals processed by the second processor from a second communication link terminal deployable with the second satellite. A first switch, deployable with the first satellite, enables signals from the uplink receiver to be utilized by the first intersatellite communication link terminal or the first processor. A downlink transmitter, deployable with the first satellite, is capable of transmitting signals to a ground based communication station. A second switch, deployable with the first satellite, enables signals from the first intersatellite link terminal or the first processor to be utilized by the downlink transmitter.
By employing apparatus of the foregoing type, the processor capabilities of the first satellite can be enhanced by launching the second satellite, preferably into the orbital slot of the first satellite. The new processing functionality can be performed on the second satellite and the results transmitted to the first satellite for communication through the downlink transmitter to the ground based communication station. By using apparatus and methods of the foregoing type, the processing functionality of the satellite communication system can be altered and modified with a degree of ease and economy and not available by the use of the known prior techniques.